Image blur correction device, imaging apparatus, image blur correction method, and image blur correction program

ABSTRACT

The image blur correction device includes an acceleration sensor, an angular velocity sensor, and a system control unit. The system control unit selects one of rotation axes based on a usage state of a digital camera, and calculates a shift blur amount generated in a direction by rotation of the digital camera around a second axis and a shift blur amount generated in a direction by rotation of the digital camera around a first axis based on distances from the selected rotation axis to the acceleration sensor, angular velocities, and accelerations.

CROSS REFERENCE TO RELATED APPLICATION

This is a continuation of International Application No.PCT/JP2019/021624 filed on May 30, 2019, and claims priority fromJapanese Patent Application No. 2018-122367 filed on Jun. 27, 2018, theentire disclosures of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an image blur correction device, animaging apparatus, an image blur correction method, and a computerreadable medium storing an image blur correction program.

2. Description of the Related Art

An imaging apparatus comprising an imaging element for imaging a subjectthrough an imaging optical system has an image blur correction functionof correcting a blur (hereinafter, also referred to as an image blur) ofa captured image signal caused by vibration of the apparatus. The imageblur includes a shift blur, and a rotation blur.

The shift blur is a blur of the captured image signal in a directionalong each of two orthogonal sides of a light receiving surface of theimaging element, and includes a blur (hereinafter, referred to as atranslation blur) of the captured image signal caused by a translationalmotion of the apparatus and a blur (hereinafter, referred to as anangular blur) of the captured image signal caused by rotations (referredto as a pitch rotation and a yaw rotation) of the apparatus around tworotation axes which are perpendicular to an optical axis of the imagingoptical system and are orthogonal to each other.

The rotation blur is a blur of the captured image signal caused byrotation (also referred to as a roll rotation) of the apparatus around arotation axis parallel to the optical axis of the imaging opticalsystem.

JP2012-088466A and JP2012-247544A describe cameras capable of correctingthe angular blur.

SUMMARY OF THE INVENTION

In a case where a distance from a rotation center during the pitchrotation of the imaging apparatus to a principal point position of theimaging optical system is a radius of gyration Ly and a rotation angleduring the pitch rotation of the imaging apparatus is θy, a shift blurSy caused by the pitch rotation can be obtained by the calculation ofSy=Ly·tan θy.

Similarly, in a case where a distance from a rotation center during theyaw rotation of the imaging apparatus to a principal point position ofthe imaging optical system is a radius of gyration Lx and a rotationangle during the yaw rotation of the imaging apparatus is θx, a shiftblur Sx caused by the yaw rotation can be obtained by the calculation ofSx=Lx·tan θx.

An angular velocity sensor is provided in the imaging apparatus, and therotation angle θx and the rotation angle θy can be obtained based onangular velocities detected by the angular velocity sensor.

The radius of gyration Lx and the radius of gyration Ly can be obtainedbased on accelerations generated by the yaw rotation and the pitchrotation of the imaging apparatus and the angular velocities detected bythe angular velocity sensor.

However, in a case where it is assumed that the imaging apparatusyaw-rotates or pitch-rotates and roll-rotates at the same time, anacceleration sensor detects the acceleration caused by the roll rotationof the imaging apparatus in addition to the acceleration caused by theyaw rotation or pitch rotation of the imaging apparatus. In a case wherethe acceleration caused by the roll rotation is detected as describedabove, an error may be generated between the radius of gyration Lx andthe radius of gyration Ly calculated based on the acceleration, andthere is a possibility that correction accuracy of the shift blurdegrades.

In a case where a position of the rotation center the roll rotation ofthe imaging apparatus is predetermined, it is possible to accuratelycorrect the shift blur by using the radius of gyration having no errorby arranging the acceleration sensor such that an error is not generatedin either the radius of gyration Lx or the radius of gyration Ly.However, in an actual usage scene, the position of this rotation centermay change rather than being constant. JP2012-088466A and JP2012-247544Ado not consider such a change in the position of the rotation center.

The present invention has been made in view of the above circumstances,and an object of the present invention is to provide an image blurcorrection device capable of correcting a blur of a captured imagesignal caused by a pitch rotation and a yaw rotation of an imagingapparatus with high accuracy, an imaging apparatus comprising the imageblur correction device, an image blur correction method, and a computerreadable medium storing an image blur correction program.

An image blur correction device according to an embodiment of thepresent invention is an image blur correction device configured tocorrect a blur of a captured image signal output from an image sensorwhich images a subject through an imaging optical system. The devicecomprises an acceleration sensor that detects a first acceleration inone direction of two directions which are orthogonal to an optical axisof the imaging optical system of an imaging apparatus including theimage sensor and are orthogonal to each other and a second accelerationin the other direction of the two directions, an angular velocity sensorthat detects a first angular velocity of the imaging apparatus around afirst axis parallel to the other direction and a second angular velocityof the imaging apparatus around a second axis parallel to the onedirection, a radius-of-gyration calculator that calculates a firstradius of gyration of the imaging apparatus around the first axis basedon the first acceleration and the first angular velocity and a secondradius of gyration of the imaging apparatus around the second axis basedon the second acceleration and the second angular velocity, and acorrector that calculates a first blur amount of the captured imagesignal in the one direction generated by rotation of the imagingapparatus around the first axis based on the first angular velocity andat least one of the first radius of gyration or the second radius ofgyration, calculates a second blur amount of the captured image signalin the other direction generated by rotation of the imaging apparatusaround the second axis based on the second angular velocity and at leastone of the first radius of gyration or the second radius of gyration,and corrects the calculated first blur amount and the calculated secondblur amount. The corrector selects one rotation axis from among aplurality of rotation axes determined in advance parallel to the opticalaxis based on a usage state of the imaging apparatus, and determines thefirst radius of gyration and the second radius of gyration used incalculating the first blur amount and the second blur amount based ondistances in the two directions from the selected rotation axis to theacceleration sensor.

An imaging apparatus according to an embodiment of the present inventioncomprises the image blur correction device and the image sensor.

An image blur correction method according to an embodiment of thepresent invention is an image blur correction method of correcting ablur of a captured image signal output from an image sensor which imagesa subject through an imaging optical system. The method comprises aradius-of-gyration calculation step of calculating a first radius ofgyration of an imaging apparatus around a first axis based on a firstacceleration and a first angular velocity detected by an accelerationsensor that detects the first acceleration in one direction of twodirections which are orthogonal to an optical axis of the imagingoptical system of the imaging apparatus including the image sensor andare orthogonal to each other and a second acceleration in the otherdirection of the two directions and an angular velocity sensor thatdetects the first angular velocity of the imaging apparatus around thefirst axis parallel to the other direction and a second angular velocityof the imaging apparatus around a second axis parallel to the onedirection, and calculating a second radius of gyration of the imagingapparatus around the second axis based on the second acceleration andthe second angular velocity, and a correction step of calculating afirst blur amount of the captured image signal in the one directiongenerated by rotation of the imaging apparatus around the first axisbased on the first angular velocity and at least one of the first radiusof gyration or the second radius of gyration, calculating a second bluramount of the captured image signal in the other direction generated byrotation of the imaging apparatus around the second axis based on thesecond angular velocity and at least one of the first radius of gyrationor the second radius of gyration, and correcting the calculated firstblur amount and the calculated second blur amount. In the correctionstep, one rotation axis is selected from among a plurality of rotationaxes determined in advance parallel to the optical axis based on a usagestate of the imaging apparatus, and the first radius of gyration and thesecond radius of gyration used in calculating the first blur amount andthe second blur amount is determined based on distances in the twodirections from the selected rotation axis to the acceleration sensor.

A non-transitory computer readable medium storing an image blurcorrection program according to an embodiment of the present inventionis an image blur correction program for correcting a blur of a capturedimage signal output from an image sensor which images a subject throughan imaging optical system. The program causes a computer to execute aradius-of-gyration calculation step of calculating a first radius ofgyration of an imaging apparatus around a first axis based on a firstacceleration and a first angular velocity detected by an accelerationsensor that detects the first acceleration in one direction of twodirections which are orthogonal to an optical axis of the imagingoptical system of the imaging apparatus including the image sensor andare orthogonal to each other and a second acceleration in the otherdirection of the two directions and an angular velocity sensor thatdetects the first angular velocity of the imaging apparatus around thefirst axis parallel to the other direction and a second angular velocityof the imaging apparatus around a second axis parallel to the onedirection, and calculating a second radius of gyration of the imagingapparatus around the second axis based on the second acceleration andthe second angular velocity, and a correction step of calculating afirst blur amount of the captured image signal in the one directiongenerated by rotation of the imaging apparatus around the first axisbased on the first angular velocity and at least one of the first radiusof gyration or the second radius of gyration, calculating a second bluramount of the captured image signal in the other direction generated byrotation of the imaging apparatus around the second axis based on thesecond angular velocity and at least one of the first radius of gyrationor the second radius of gyration, and correcting the calculated firstblur amount and the calculated second blur amount. In the correctionstep, one rotation axis is selected from among a plurality of rotationaxes determined in advance parallel to the optical axis based on a usagestate of the imaging apparatus, and the first radius of gyration and thesecond radius of gyration used in calculating the first blur amount andthe second blur amount is determined based on distances in the twodirections from the selected rotation axis to the acceleration sensor.

According to the present invention, it is possible to provide an imageblur correction device capable of correcting a blur of a captured imagesignal caused by a pitch rotation and a yaw rotation of an imagingapparatus with high accuracy, an imaging apparatus comprising the imageblur correction device, an image blur correction method, and an imageblur correction program.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view showing a schematic configuration of a digitalcamera 100 which is an embodiment of an imaging apparatus of the presentinvention.

FIG. 2 is a rear view showing a schematic configuration of the digitalcamera 100 shown in FIG. 1.

FIG. 3 is a block diagram showing a hardware configuration of thedigital camera 100 shown in FIG. 1.

FIG. 4 is a functional block diagram of a system control unit 1 shown inFIG. 3.

FIG. 5 is a schematic diagram for describing a method of calculating ashift blur amount of a captured image signal generated by a yaw rotationof the digital camera 100 around a first axis YJ.

FIG. 6 is a schematic diagram for describing a method of calculating ashift blur amount of the captured image signal generated by a rotationof the digital camera 100 around a second axis XJ.

FIG. 7 is a diagram showing a setting example of a rotation axis in thedigital camera 100 shown in FIG. 1.

FIG. 8 is a flowchart for describing an operation of the digital camera100 shown in FIG. 1 in a still image imaging mode.

FIG. 9 is a flowchart for describing a modification example of theoperation of the digital camera 100 shown in FIG. 1.

FIG. 10 is a block diagram showing a hardware configuration of asmartphone 200 which is an embodiment of the imaging apparatus of thepresent invention.

FIG. 11 is a front view showing a schematic configuration of thesmartphone 200 shown in FIG. 10.

FIG. 12 is a functional block diagram of a system control unit 1A shownin FIG. 10.

FIG. 13 is a flowchart for describing an operation of the smartphone 200shown in FIG. 10 in a still image imaging mode.

FIG. 14 is a flowchart for describing an operation of the smartphone 200shown in FIG. 10 in the still image imaging mode.

FIG. 15 is a diagram showing a hardware configuration of a smartphone200A which is a modification example of the smartphone 200 shown in FIG.10.

FIG. 16 is a flowchart for describing an operation of the smartphone200A shown in FIG. 15 in a still image imaging mode.

FIG. 17 is a diagram showing a state in which the smartphone 200A shownin FIG. 15 is gripped in portrait shooting.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present invention will be describedwith reference to the drawings.

FIG. 1 is a front view showing a schematic configuration of a digitalcamera 100 which is an embodiment of an imaging apparatus of the presentinvention. FIG. 2 is a rear view showing the schematic configuration ofthe digital camera 100 shown in FIG. 1. FIG. 3 is a block diagramshowing a hardware configuration of the digital camera 100 shown in FIG.1.

The digital camera 100 comprises a lens barrel 101 and a finder window108 a (see FIG. 1) provided on a front surface of a housing, a shutterbutton 102 a (see FIGS. 1 and 2) provided on a side surface of thehousing, a display unit 103, an eyepiece window 108 b, and an operationunit 102 b (see FIG. 2) provided on a back surface of the housing, animage sensor 20 provided in the housing, an image blur correctionmechanism 3, an analog front end (AFE) 104, an image sensor drive unit105, an angular velocity sensor 106, an acceleration sensor 107, animage processing unit 108, a memory 109, and a system control unit 1.

The lens barrel 101 has an imaging optical system 101 a therein. Theimaging optical system 101 a includes at least an imaging lens such as afocus lens or a zoom lens. The imaging optical system 101 a includes astop mechanism, a mechanical shutter mechanism, or the like asnecessary. The lens barrel 101 may be fixed to a main body of thedigital camera 100 or may be attachable to and detachable from the mainbody of the digital camera 100.

The image sensor 20 images a subject through the imaging optical system101 a, and is a charge coupled device (CCD) image sensor, acomplementary metal oxide semiconductor (CMOS) image sensor, or thelike. As shown in FIGS. 1 and 2, a light receiving surface of the imagesensor 20 has a rectangular shape.

The shutter button 102 a is an operation member for instructing that theimaging of the subject using the image sensor 20 is started. In a casewhere the shutter button 102 a is operated, an imaging instructionsignal is input to the system control unit 1. In a case where theimaging instruction signal is received, the system control unit 1controls the image sensor 20 to image the subject.

The operation unit 102 b includes a jog dial, a cross key, or a buttonfor performing various operations such as switching between a stillimage imaging mode for imaging a still image and a motion pictureimaging mode for imaging a motion picture, setting an imaging condition,or selecting an imaging menu. In a case where the operation unit 102 bis operated, various instruction signals are input to the system controlunit 1.

The finder window 108 a and the eyepiece window 108 b constitute a partof an optical finder. In a case where a user looks through the eyepiecewindow 108 b, the subject can be observed through the finder window 108a.

In the digital camera 100, an electronic viewfinder may be used insteadof the optical finder. In this case, the finder window 108 a is deleted,and an image on a display unit for observing the subject installed inthe housing of the digital camera 100 can be viewed by looking throughthe eyepiece window 108 b.

The digital camera 100 may have a hybrid finder having both functions ofthe optical finder and the electronic viewfinder. In any of the finders,the eyepiece window 108 b for the user to observe the subject isprovided on the back surface of the housing of the digital camera 100.

The display unit 103 is a liquid crystal display (LCD), an organicelectro luminescence (EL) display, or the like. In the digital camera100, in a case where an imaging mode for imaging the subject is set, alive view image is displayed on the display unit 103. Accordingly, thesubject can be observed not only by the finder described above but alsoby the display unit 103.

The image blur correction mechanism 3 images the subject by the imagesensor 20 and corrects a blur of a captured image signal output from theimage sensor 20 by moving the light receiving surface of the imagesensor 20 into a plane perpendicular to an optical axis K of the imagingoptical system 101 a.

In the digital camera 100, a state in which the light receiving surfaceof the image sensor 20 is perpendicular to a vertical direction (a statein which the optical axis K is parallel to the vertical direction) and astate in which a center of the light receiving surface is located on theoptical axis K are referred to as a reference state.

In the reference state, a longitudinal direction of the light receivingsurface of the image sensor 20 is defined as a direction X, a lateraldirection of the light receiving surface of the image sensor 20 isdefined as a direction Y, and a direction orthogonal to the direction Xand the direction Y (a direction in which an optical axis of the imagingoptical system 101 a extends) is defined as a direction Z (see FIGS. 1and 2).

The image blur correction mechanism 3 corrects at least a shift blur ofimage blurs by moving the image sensor 20 in the directions X and Y. Theshift blur includes a blur (angular blur) of the captured image signalcaused by rotations of the apparatus around each of two rotation axes(an axis extending in the direction X and an axis extending in thedirection Y) which are perpendicular to the optical axis K of theimaging optical system 101 a and are orthogonal to each other (referredto as a pitch rotation and a yaw rotation) and a blur (a translationblur) of the captured image signal caused by movement of the apparatusin the direction X and the direction Y by the rotation thereof.

The acceleration sensor 107 detects at least an acceleration in each ofthe directions X and Y which are two directions orthogonal to theoptical axis K of the imaging optical system 101 a and orthogonal toeach other. The direction X is one of the two directions. The directionY is the other direction of these two directions. Examples of theacceleration sensor 107 include a three-axis acceleration sensor thatdetects an acceleration in each of the direction X, the direction Y, andthe direction Z.

Hereinafter, the acceleration in the direction X detected by theacceleration sensor 107 is referred to as a first acceleration Atx, andthe acceleration in the direction Y detected by the acceleration sensor107 is referred to as a second acceleration Aty. The accelerationsdetected by the acceleration sensor 107 are input to the system controlunit 1.

As shown in FIG. 1, the angular velocity sensor 106 detects at least afirst angular velocity ωx around a first axis YJ parallel to thedirection Y and a second angular velocity ωy around a second axis XJparallel to the direction X. The angular velocities detected by theangular velocity sensor 106 are input to the system control unit 1.Examples of the angular velocity sensor 106 include a three-axis angularvelocity sensor that detects an angular velocity around an axis parallelto the direction X, an angular velocity around an axis parallel to thedirection Y, and an angular velocity around an axis parallel to thedirection Z.

The AFE 104 shown in FIG. 3 includes a signal processing circuit thatperforms Sampling two correlation pile processing, digital conversionprocessing, and the like on the captured image signal output from theimage sensor 20.

The image processing unit 108 shown in FIG. 3 generates captured imagedata in a Joint Photographic Experts Group (JPEG) format or the like byperforming digital signal processing on the captured image signalprocessed by the AFE 104.

The system control unit 1 shown in FIG. 3 controls the image sensordrive unit 105 and the AFE 104 to cause the image sensor 20 to image thesubject and output the captured image signal corresponding to a subjectimage from the image sensor 20. The system control unit 1 controls theimage blur correction mechanism 3 based on motion information of thedigital camera 100 detected by the acceleration sensor 107 and theangular velocity sensor 106. The system control unit 1 corrects theshift blur of the captured image signal output from the image sensor 20by moving the light receiving surface of the image sensor 20 in at leastone of the direction X or Y. The system control unit 1, the accelerationsensor 107, and the angular velocity sensor 106 constitute an image blurcorrection device.

The system control unit 1 controls the entire digital camera 100 as awhole, and is constituted by various processors that perform processingby executing a program including an image blur correction program.

A central processing unit (CPU) which is a general-purpose processorthat performs various kinds of processing by executing a program, aprogrammable logic device (PLD) which is a processor capable of changinga circuit configuration after a field programmable gate array (FPGA) ismanufactured, a dedicated electric circuit which is a processor having acircuit configuration specifically designed to execute specificprocessing such as an application specific integrated circuit (ASIC), orthe like is included as various processors.

More specifically, structures of these various processors are electriccircuits in which circuit elements such as semiconductor elements arecombined.

The system control unit 1 may be constituted by one of variousprocessors, or may be constituted by a combination of two or moreprocessors of the same type or different types (for example, acombination of a plurality of FPGAs or a combination of a CPU and anFPGA).

The memory 109 includes a random access memory (RAM) and a read onlymemory (ROM). The ROM stores programs (including an image blurcorrection program) necessary for an operation of the system controlunit 1 and various kinds of data.

FIG. 4 is a functional block diagram of the system control unit 1 shownin FIG. 3. The system control unit 1 functions as a radius-of-gyrationcalculator 11 and a corrector 12 by executing a program including theimage blur correction program stored in the ROM of the memory 109.

The radius-of-gyration calculator 11 calculates a first radius ofgyration Lx in a case where the digital camera 100 rotates around thefirst axis YJ (yaw rotation) based on the first acceleration Atx and thefirst angular velocity ωx, and calculates a second radius of gyration Lyin a case where the digital camera 100 rotates around the second axis XJ(pitch rotation) based on the second acceleration Aty and the secondangular velocity ωy.

FIG. 5 is a schematic diagram for describing a method of calculating ashift blur amount of the captured image signal caused by the rotation ofthe digital camera 100 around the first axis YJ. FIG. 5 shows a state inwhich the digital camera 100 is viewed from the direction Y.

As shown in FIG. 5, in a case where the digital camera 100 yaw-rotatesaround the first axis YJ by a rotation angle θx and moves to a positionindicated by a broken line, the first radius of gyration Lx in a casewhere the digital camera 100 yaw-rotates can be calculated by thefollowing Equation (A).

Lx=Vx/ωx  (A)

In Equation (A), “Vx” is a velocity obtained by integrating the firstacceleration Atx in the direction X generated by the yaw rotation. Thefirst radius of gyration Lx is defined by a distance in the direction Zbetween a rotation center RS in a case where the digital camera 100yaw-rotates and a principal point position P of the imaging opticalsystem 101 a of the digital camera 100.

As shown in FIG. 5, in a case where the digital camera 100 yaw-rotates,a subject H present on the optical axis before the yaw rotation ispresent at a position separated from the optical axis in the direction Xby Sx after the yaw rotation. This Sx is a shift blur amount (first bluramount) of the captured image signal generated in the direction X due tothe yaw rotation. The shift blur amount Sx can be calculated by thecalculation of the following Equation (B).

Sx=Lx·tan θx  (B)

The rotation angle θx shown in FIG. 5 can be obtained by integrating thefirst angular velocity ωx detected by the angular velocity sensor 106.

FIG. 6 is a schematic diagram for describing a method of calculating ashift blur amount of the captured image signal generated by the rotationof the digital camera 100 around the second axis XJ. FIG. 6 shows astate in which the digital camera 100 is viewed from the direction X. Asshown in FIG. 6, in a case where the digital camera 100 pitch-rotatesaround the second axis XJ by the rotation angle θy and moves to aposition indicated by a broken line, the second radius of gyration Ly ina case where the digital camera 100 pitch-rotates can be calculated bythe following Equation (C).

Ly=Vy/ωy  (C)

In Equation (C), “Vy” is a velocity obtained by integrating the secondacceleration Aty in the direction Y generated by the pitch rotation. Thesecond radius of gyration Ly is defined by a distance in the direction Zbetween the rotation center RS in a case where the digital camera 100pitch-rotates and the principal point position P of the imaging opticalsystem 101 a of the digital camera 100.

As shown in FIG. 6, in a case where the digital camera 100pitch-rotates, the subject H present on the optical axis before thepitch rotation is present at a position separated from the optical axisby Sy in the direction Y after the pitch rotation. This Sy is a shiftblur amount (second blur amount) of the captured image signal generatedin the direction Y due to the pitch rotation. The shift blur amount Sycan be calculated by the calculation of the following Equation (D).

Sy=Ly·tan θy  (D)

The rotation angle θy shown in FIG. 6 can be obtained by integrating thesecond angular velocity ωy detected by the angular velocity sensor 106.

As described above, the shift blur amount Sx generated by the yawrotation of the digital camera 100 can be calculated based on the firstangular velocity ωx and the first radius of gyration Lx, and the firstradius of gyration Lx can be calculated based on the first accelerationAtx.

The shift blur amount Sy generated by the pitch rotation of the digitalcamera 100 can be calculated based on the second angular velocity ωy andthe second radius of gyration Ly, and the second radius of gyration Lycan be calculated based on the second acceleration Aty.

In a case where general imaging is assumed, it is difficult to considerthat a large difference is generated between the first radius ofgyration Lx and the second radius of gyration Ly. However, in a casewhere it is considered that the digital camera 100 yaw-rotates orpitch-rotates and roll rotation at the same time, the accelerationsensor 107 detects, an error, the acceleration caused by the rollrotation of the digital camera 100 (rotational acceleration component)in addition to the acceleration due to the yaw rotation or pitchrotation of the digital camera 100. Due to the influence of this error,there is a possibility that a difference in accuracy between the firstradius of gyration Lx and the second radius of gyration Ly obtained fromthe acceleration.

Although a relationship between the rotational acceleration componentincluded in the first acceleration Atx and the rotational accelerationcomponent included in the second acceleration Aty is determined by apositional relationship between the acceleration sensor 107 and therotation center (rotation axis) in a case where the digital camera 100roll-rotates, this rotation axis may change depending on the usage stateof the digital camera 100.

In the digital camera 100, a rotation axis R1 and a rotation axis R2 areset in advance as rotation axes in a case where the digital camera 100roll-rotates as shown in FIG. 7.

The rotation axis R1 is an axis extending in the direction Z and set atthe same position as the optical axis K of the imaging optical system101 a. The rotation axis R2 is an axis extending in the direction Z andset at a position of the eyepiece window 108 b. A position of therotation axis R2 is set at a center of the eyepiece window 108 b in theexample of FIG. 7, but this position may be any position in a range inwhich the rotation axis overlaps the eyepiece window 108 b.

It is assumed that the user of the digital camera 100 images the subjectby pressing the shutter button 102 a while viewing the live view imagedisplayed on the display unit 103 and observing the subject. In thiscase, it is considered that a rotation center in a case where thedigital camera 100 roll-rotates is substantially coincident with aposition of the optical axis K of the imaging optical system 101 a.Thus, the rotation axis R1 is set at the same position as the opticalaxis K of the imaging optical system 101 a.

It is assumed that the user of the digital camera 100 images the subjectby pressing the shutter button 102 a while observing the subject withone eye on the eyepiece window 108 b. In this case, it is consideredthat the rotation center in a case where the digital camera 100roll-rotates is substantially coincident with the position of theeyepiece window 108 b. Thus, the rotation axis R2 is set at the positionof the eyepiece window 108 b.

For example, it is assumed that the digital camera 100 roll-rotatesaround the rotation axis R1. In this case, a distance x1 between therotation axis R1 and the acceleration sensor 107 in the direction X isgreater than a distance y1 between the rotation axis R1 and theacceleration sensor 107 in the direction Y.

Thus, an error component of the acceleration generated in the directionX due to the roll rotation around the rotation axis R1 is less than anerror component of the acceleration generated in the direction Y. Thatis, in this case, the first radius of gyration Lx becomes closer to anaccurate value than the second radius of gyration Ly.

Meanwhile, it is assumed that the digital camera 100 roll-rotates aroundthe rotation axis R2. In this case, a distance x2 between the rotationaxis R2 and the acceleration sensor 107 in the direction X is less thana distance y2 between the rotation axis R2 and the acceleration sensor107 in the direction Y.

Thus, the error component of the acceleration generated in the directionX due to the roll rotation around the rotation axis R2 is greater thanthe error component of the acceleration generated in the direction Y.That is, in this case, the second radius of gyration Ly becomes closerto a more accurate value than the first radius of gyration Lx.

For example, it is assumed that the acceleration sensor 107 is arrangedsuch that the distance x1 and the distance y1 shown in FIG. 7 are thesame. In this configuration, in a case where it is assumed that thedigital camera 100 roll-rotates around the rotation axis R1, there isalmost no difference in accuracy between the first radius of gyration Lxand the second radius of gyration Ly.

As described above, the difference in accuracy between the first radiusof gyration Lx and the second radius of gyration Ly is generateddepending on the positional relationship between the acceleration sensor107 and the rotation axis in a case where the digital camera 100roll-rotates. It is considered that the first radius of gyration Lx andthe second radius of gyration Ly are the same in the general imaging.

That is, in the calculation of the shift blur amounts Sx and Sydescribed above, for example, the shift blur amounts Sx and Sy can beaccurately calculated by using one of the first radius of gyration Lxand the second radius of gyration Ly which is considered to be moreaccurate even though there is an error in acceleration due to the rollrotation.

Due to the use of a more accurate radius of gyration, the corrector 12shown in FIG. 4 calculates the shift blur amount Sx based on the firstangular velocity ωx and at least one of the first radius of gyration Lxor the second radius of gyration Ly, and calculates the shift bluramount Sy based on the second angular velocity ωy and at least one ofthe first radius of gyration Lx or the second radius of gyration Ly.

The corrector 12 selects one of the rotation axes R1 and R2 shown inFIG. 7 based on the usage state of the digital camera 100, anddetermines the radius of gyration used in the calculation of the shiftblur amount Sx and the shift blur amount Sy based on a first distance pxin the direction X and a second distance py in the direction Y from theselected rotation axis R1 or rotation axis R2 to the acceleration sensor107.

The corrector 12 corrects the shift blurs of the captured image signalin the directions X and Y by controlling the image blur correctionmechanism 3 so as to cancel the shift blur amounts Sx and Sy calculatedin this manner.

The rotation axis to be selected by the corrector 12 is determined inadvance according to the usage state of the digital camera 100. Theusage state indicates a state in which the digital camera 100 is used ina case where an imaging instruction to instruct that the imaging of thesubject is started while the digital camera 100 is set in the imagingmode. In the digital camera 100, this usage state includes a usage statein which the subject is observed by using the eyepiece window 108 b anda usage state in which the subject is observed without using theeyepiece window 108 b.

FIG. 8 is a flowchart for describing an operation of the digital camera100 shown in FIG. 1 in the still image imaging mode. The shutter button102 a is pressed in a state in which the still image imaging mode isset, the operation shown in FIG. 8 is started.

First, the corrector 12 of the system control unit 1 determines whetheror not the subject is being observed by using the eyepiece window 108 b(step S1).

For example, a contact sensor is provided at the eyepiece window 108 b.In a case where the contact of an object is detected by the contactsensor, the corrector 12 determines that the subject is being observedby using the eyepiece window 108 b. Meanwhile, in a case where thecontact of the object is not detected by the contact sensor, thecorrector 12 determines that the subject is observed without using theeyepiece window 108 b.

In a case where the eyepiece window 108 b of the digital camera 100constitutes a part of the electronic viewfinder, a switch for turning onand off the function of the electronic viewfinder may be included in theoperation unit 102 b instead of the contact sensor.

The corrector 12 may determine that the subject is being observed byusing the eyepiece window 108 b in a case where the function of theelectronic viewfinder is turned on by this switch, and may determinethat the subject is being observed without using the eyepiece window 108b in a case where the function of the electronic viewfinder is turnedoff by this switch.

In a case where it is determined that the subject is being observed byusing the eyepiece window 108 b (step S1: YES), the corrector 12 selectsthe rotation axis R2 shown in FIG. 7 set at the position of the eyepiecewindow 108 b (step S2).

In a case where it is determined that the subject is being observedwithout using the eyepiece window 108 b (step S1: NO), the corrector 12selects the rotation axis R1 shown in FIG. 5 set at the same position asthe optical axis K (step S3).

After step S2 or step S3, the system control unit 1 acquires the firstacceleration ATx and the second acceleration Aty from the accelerationsensor 107, and acquires the first angular velocity ωx and the secondangular velocity ωy from the angular velocity sensor 106 (step S4).

Subsequently, the radius-of-gyration calculator 11 of the system controlunit 1 calculates the first radius of gyration Lx by the calculation ofEquation (A) based on the first acceleration Atx and the first angularvelocity ωx acquired in step S4, and calculates the second radius ofgyration Ly by the calculation of Equation (C) based on the secondacceleration Aty and the second angular velocity ωy acquired in step S4(step S5).

Subsequently, the corrector 12 calculates the difference between thefirst distance px in the direction X and the second distance py in thedirection Y between the rotation axis selected in step S2 or step S3 andthe acceleration sensor 107, and determines whether or not thisdifference is less than a predetermined threshold value TH (step S6).Information on the first distance px and the second distance py in thedirections X and Y between the rotation axis R1 or R2 and theacceleration sensor 107 is stored in advance in the ROM of the memory109.

In a case where it is determined that the difference is less than thethreshold value TH (step S6: YES), the corrector 12 calculates the shiftblur amounts Sx and Sy by using both the first radius of gyration Lx andthe second radius of gyration Ly calculated in step S5.

Specifically, the corrector 12 calculates the shift blur amount Sx bysubstituting an average value of the first radius of gyration Lx and thesecond radius of gyration Ly calculated in step S5 into “Lx” in Equation(B). Similarly, the corrector 12 calculates the shift blur amount Sy bysubstituting an average value of the first radius of gyration Lx and thesecond radius of gyration Ly calculated in step S5 into “Ly” of Equation(D) (step S7).

In a case where it is determined that the difference is equal to orgreater than the threshold value TH (step S6: NO), the corrector 12determines whether or not the first distance px is greater than thesecond distance py (step S8).

In a case where the first distance px is greater than the seconddistance py (step S8: YES), the corrector 12 calculates the shift bluramounts Sx and Sy by using only the first radius of gyration Lxcalculated in step S5.

Specifically, the corrector 12 calculates the shift blur amount Sx bysubstituting the first radius of gyration Lx calculated in step S5 into“Lx” in Equation (B), and calculates the shift blur amount Sy bysubstituting the first radius of gyration Lx calculated in step S5 into“Ly” in Equation (D) (step S9).

In a case where the first distance px is less than the second distancepy (step S8: NO), the corrector 12 calculates the shift blur amounts Sxand Sy by using only the second radius of gyration Ly calculated in stepS5.

Specifically, the corrector 12 calculates the shift blur amount Sx bysubstituting the second radius of gyration Ly calculated in step S5 into“Lx” in Equation (B), and calculates the shift blur amount Sy bysubstituting the second radius of gyration Ly calculated in step S5 into“Ly” in Equation (D) (step S10).

The corrector 12 calculates the shift blur amounts Sx and Sy in step S7,step S9, or step S10, and corrects the shift blur of the captured imagesignal output from the image sensor 20 by controlling the image blurcorrection mechanism 3 so as to cancel the shift blur amounts Sx and Sy(step S11).

As described above, the digital camera 100 selects the rotation axisassumed to be the rotation center in a case where the digital camera 100roll-rotates, and determines whether the shift blur amounts Sx and Syare calculated by using only the first radius of gyration Lx, the shiftblur amounts Sx and Sy are calculated by using only the second radius ofgyration Ly, or the shift blur amounts Sx and Sy are calculated by usingboth the first radius of gyration Lx and the second radius of gyrationLy based on the distance between this rotation axis and the accelerationsensor 107.

In a case where the difference between the first distance px and thesecond distance py between the selected rotation axis and theacceleration sensor 107 is less than the threshold value TH, it ispossible to determine that there is no difference in accuracy betweenthe first radius of gyration Lx and the second radius of gyration Ly.Thus, in this case, it is assumed that the calculation accuracy of theshift blur amounts Sx and Sy can be improved by calculating the shiftblur amounts Sx and Sy by using both the first radius of gyration Lx andthe second radius of gyration Ly even though the digital cameraroll-rotates during the pitch rotation or the yaw rotation.

In a case where the difference between the first distance px and thesecond distance py between the selected rotation axis and theacceleration sensor 107 is equal to or greater than the threshold valueTH and the first distance px is greater than the second distance py (forexample, in a case where the rotation axis R1 is selected), it ispossible to determine that the first radius of gyration Lx is closer tothe accurate value than the second radius of gyration Ly as describedabove. Thus, in this case, the calculation accuracy of the shift bluramounts Sx and Sy can be calculated by calculating the shift bluramounts Sx and Sy by using only the first radius of gyration Lx eventhough the digital camera roll-rotates during the pitch rotation or theyaw rotation.

In a case where the difference between the first distance px and thesecond distance py between the selected rotation axis and theacceleration sensor 107 is equal to or greater than the threshold valueTH and the first distance px is less than the second distance py (forexample, in a case where the rotation axis R2 is selected), it ispossible to determine that the second radius of gyration Ly is closer tothe accurate value than the first radius of gyration Lx as describedabove. Thus, in this case, the calculation accuracy of the shift bluramounts Sx and Sy can be improved by calculating the shift blur amountsSx and Sy using only the second radius of gyration Ly even though thedigital camera roll-rotates during the pitch rotation or the yawrotation.

In step S7, the corrector 12 may calculate the shift blur amount Sx bysubstituting the second radius of gyration Ly calculated in step S5 into“Lx” in Equation (B), and may calculate the shift blur amount Sy bysubstituting the first radius of gyration Lx calculated in step S5 into“Ly” in Equation (D). By doing so, it is possible to improve thecalculation accuracy of the shift blur amounts Sx and Sy by absorbingthe difference between the radius of gyration caused by a slightdifference between the first distance px and the second distance py.

FIG. 9 is a flowchart for describing a modification example of theoperation of the digital camera 100 shown in FIG. 1. The flowchart shownin FIG. 9 shows an operation after the shutter button 102 a is pressedin a state in which the still image imaging mode or the motion pictureimaging mode is set.

The flowchart shown in FIG. 9 is the same as FIG. 8 except that step S0is added. The same processing in FIG. 9 as that in FIG. 8 is denoted bythe same reference, and the description is omitted.

After the shutter button 102 a is pressed, in step S0, the corrector 12of the system control unit 1 determines whether or not the imaging modeis the motion picture imaging mode. The corrector 12 moves theprocessing to step S3 in a case where the imaging mode is the motionpicture imaging mode (step S0: YES), and proceeds to step S1 in a casewhere the imaging mode is the still image imaging mode (step S0: NO).

According to the operation of the modification example described above,in the motion picture imaging mode, the rotation axis R1 is selectedregardless of the usage state of the digital camera 100. The influenceon the accelerations in the directions X and Y due to the roll rotationthat can occur by pressing the shutter button 102 a of the digitalcamera 100 is large in the still image imaging mode in which exposure isperformed only once immediately after the shutter button 102 a ispressed.

In the motion picture imaging mode, since the imaging is continuouslyperformed after the shutter button 102 a is pressed, the roll rotationoccurs by pressing the shutter button 102 a, and the influence on thecaptured image is slight even though there is the error in accelerationdue to the roll rotation.

Since the imaging is performed while the digital camera 100 is held byboth hands during the imaging of the motion picture in many cases, it isconsidered that the digital camera 100 easily roll-rotates around therotation axis R1. Thus, the shift blur can be corrected with highaccuracy by selecting the rotation axis R1 during the motion pictureimaging.

FIG. 10 is a block diagram showing a hardware configuration of asmartphone 200 which is an embodiment of the imaging apparatus of thepresent invention. FIG. 11 is a front view showing a schematicconfiguration of the smartphone 200 shown in FIG. 10. The samecomponents in FIG. 10 as those in FIG. 3 are denoted by the samereferences.

The smartphone 200 shown in FIG. 10 is the same as the digital camera100 of FIG. 3 except that the system control unit 1 is changed to asystem control unit 1A by adding a touch panel 201, a communication unit202, a button 202 a, and a button 202 b and deleting the shutter button102 a and the operation unit 102 b. The communication unit 202 is afunctional unit for performing near field communication or datacommunication via a mobile phone network.

As shown in FIG. 11, the display unit 103 is formed on a front surfaceof a housing of the smartphone 200, and the touch panel 201 isintegrally formed on the display unit 103. The imaging optical system101 a is formed on a back surface of the housing of the smartphone 200(a surface opposite to the front surface on which the display unit 103is formed).

In the smartphone 200, a state in which the light receiving surface ofthe image sensor 20 is perpendicular to the vertical direction (a statein which the optical axis K is parallel to the vertical direction) and astate in which the center of the light receiving surface is located onthe optical axis K is referred to as a reference state. In thisreference state, a longitudinal direction of the light receiving surfaceof the image sensor 20 is defined as a direction X, a lateral directionof the light receiving surface of the image sensor 20 is defined as adirection Y, and a direction orthogonal to the direction X and thedirection Y (a direction in which an optical axis of the imaging opticalsystem 101 a extends) is defined as a direction Z.

A planar shape of the display unit 103 viewed from the direction Z isrectangular. The longitudinal direction of the display unit 103 is thedirection Y, and the lateral direction of the display unit 103 is thedirection X.

As shown in FIG. 11, the button 202 a is formed on an upper end of thehousing of the smartphone 200 in the direction Y. The button 202 b isformed on a right end of the housing of the smartphone 200 in thedirection X.

The button 202 a and the button 202 b each function as a shutter buttonfor instructing that the imaging of the subject is started in a state inwhich a camera application of the smartphone 200 is activated and thesmartphone 200 shifts to the imaging mode. The button 202 a and thebutton 202 b each constitute an operation member provided at a positiondifferent from the display unit 103.

In the smartphone 200, a rotation axis R3, a rotation axis R4, and arotation axis R5 are set as rotation axes in a case where the smartphone200 rotates (roll-rotates) around the rotation axis parallel to theoptical axis K in advance as shown in FIG. 11.

The rotation axis R5 is an axis extending in the direction Z and set atthe center of the display unit 103. The rotation axis R3 is an axisextending in the direction Z and set near the upper end in the directionY at the left end of the housing of the smartphone 200 in the directionX. The rotation axis R4 is an axis extending in the direction Z and setnear the left end in the direction X at a lower end of the housing ofthe smartphone 200 in the direction Y.

The rotation axis R3 and the rotation axis R4 form two rotation axespresent at positions different from the optical axis K. The rotationaxis R3 is one rotation axis of the two rotation axes, and the rotationaxis R4 is the other rotation axis of the two rotation axes.

Unlike the digital camera 100 of FIG. 1, the smartphone 200 does nothave the eyepiece window. Thus, in a case where the smartphone 200shifts to the imaging mode, the live view image captured by the imagesensor 20 is displayed on the display unit 103.

In a case where so-called portrait shooting is performed by thesmartphone 200, a posture of the smartphone 200 is determined such thatthe longitudinal direction of the display unit 103 (that is, thedirection Y) and the vertical direction are substantially parallel. In acase where so-called landscape shooting is performed by the smartphone200, the posture of the smartphone 200 is determined such that thelateral direction of the display unit 103 (that is, the direction X) andthe vertical direction are substantially parallel.

In the state in which the posture of the smartphone 200 is determinedsuch that the longitudinal direction (direction Y) of the display unit103 and the vertical direction are substantially parallel to each other,the user determines a composition while holding the vicinity of thebutton 202 a with a right finger and supporting the vicinity of therotation axis R4 with a left finger. The user images the subject bypressing the button 202 a in the direction Y. As described above, in acase where it is assumed that the portrait shooting is performed byusing the button 202 a, there is a high possibility that the smartphone200 roll-rotates around the vicinity of the left finger supporting thesmartphone 200. The rotation axis R4 is set at a position substantiallyon a diagonal line of the button 202 a on the assumption of such a case.

In the state in which the posture of the smartphone 200 is determinedsuch that the lateral direction (direction X) of the display unit 103and the vertical direction are substantially parallel to each other, theuser determines a composition while holding the vicinity of the button202 b with the right finger and supporting the vicinity of the rotationaxis R3 with the left finger. The user images the subject by pressingthe button 202 b in the direction X. As described above, in a case whereit is assumed that the landscape shooting is performed by using thebutton 202 b, there is a high possibility that the smartphone 200roll-rotates around the vicinity of the left finger supporting thesmartphone 200. The rotation axis R3 is set at a position substantiallyon a diagonal line of the button 202 b on the assumption of such a case.

The imaging instruction can be issued to the system control unit 1A byoperating the touch panel 201 without using the buttons 202 a and 202 bin a state in which the smartphone 200 shifts to the imaging mode. Asdescribed above, in a case where the imaging is performed by operatingthe touch panel 201, the housing of the smartphone 200 is firmly grippedby both hands in many cases. Thus, in this case, there is a highpossibility that the smartphone 200 roll-rotates around the center ofthe display unit 103. The rotation axis R5 is set at the center of thedisplay unit 103 on the assumption of such a case.

FIG. 12 is a functional block diagram of the system control unit 1Ashown in FIG. 10. The system control unit 1A functions as aradius-of-gyration calculator 11A and a corrector 12A by executing aprogram including the image blur correction program stored in the ROM ofthe memory 109. In the smartphone 200, the system control unit 1A, theacceleration sensor 107, and the angular velocity sensor 106 constitutethe image blur correction device.

A function of the radius-of-gyration calculator 11A is the same as thatof the radius-of-gyration calculator 11 of FIG. 4.

A function of the corrector 12A is almost the same as that of thecorrector 12 of FIG. 4, but is different from the corrector 12 in thatthe rotation axis to be selected is any of the rotation axes R3, R4, andR5 shown in FIG. 11.

Specifically, the corrector 12A selects the rotation axis R5 in theusage state in which the imaging is performed by operating the touchpanel 201 (so-called touch imaging), selects the rotation axis R4 in theusage state in which the imaging is performed by operating the button202 a and the direction Y is the vertical direction (state of so-calledportrait shooting), and selects the rotation axis R3 in the usage statein which the imaging is performed by operating the button 202 b and thedirection X is the vertical direction (state of so-called landscapeshooting).

The usage state of the smartphone 200 indicates a state in which thesmartphone 200 is used in a case where the imaging mode is set. In thesmartphone 200, the usage state includes a state in which the touchimaging is performed, a state in which the button is operated in theportrait shooting, and a state in which the button is operated in thelandscape shooting.

FIGS. 13 and 14 are flowcharts for describing an operation of thesmartphone 200 shown in FIG. 10 in the still image imaging mode.

In a case where the imaging instruction is given by the operation of thetouch panel 201 (step S21: YES), the corrector 12A of the system controlunit 1A selects the rotation axis R5 set at the center of the displayunit 103 (step S22).

In a case where the imaging instruction is not given by the operation ofthe touch panel 201 (step S21: NO), the corrector 12A determines whetheror not the imaging instruction is given by the operation of either thebutton 202 a or the button 202 b (step S23).

In a case where the imaging instruction is not given by the operation ofeither the button 202 a or the button 202 b, the corrector 12A returnsthe processing to step S21 (step S23: NO).

In a case where the imaging instruction is given by the operation ofeither the button 202 a or the button 202 b (step S23: YES), thecorrector 12A determines whether or not the posture of the smartphone200 is either of a landscape shooting posture in which the direction Xis the vertical direction or a portrait shooting posture in which thedirection Y is the vertical direction based on a detection signal of theacceleration sensor 107 (step S24).

As a result of the determination in step S24, in a case where it is notpossible to discriminate between the portrait shooting posture and thelandscape shooting posture (step S25: YES), the corrector 12A selectsthe rotation axis R5 in step S22.

As the result of the determination in step S24, in a case where it isdetermined that the posture is the portrait shooting posture (step S26:portrait shooting), the corrector 12A selects the rotation axis R4 setat the position on the assumption of the portrait shooting (step S27).

As the result of the determination in step S24, in a case where it isdetermined that the posture is the landscape shooting posture (step S26:landscape shooting), the corrector 12A selects the rotation axis R3 setat the position on the assumption of the landscape shooting (step S28).

After the rotation axis is selected in any of step S22, step S27, andstep S28, the system control unit 1A acquires the first acceleration Atxand the second acceleration Aty from the acceleration sensor 107, andacquires the first angular velocity cox and the second angular velocityωy from the angular velocity sensor 106 (step S29).

Subsequently, the radius-of-gyration calculator 11A calculates the firstradius of gyration Lx by the calculation of Equation (A) based on thefirst acceleration Atx and the first angular velocity cox acquired instep S29, and calculates the second radius of gyration Ly by thecalculation of Equation (C) based on the second acceleration Aty and thesecond angular velocity ωy acquired in step S29 (step S30).

Subsequently, the corrector 12A calculates the difference between thefirst distance px in the direction X and the second distance py in thedirection Y between the rotation axis selected in any of step S22, stepS27, and step S28 and the acceleration sensor 107, and determineswhether or not the difference is less than the threshold value TH (stepS31). Information on the first distance px and the second distance py inthe directions X and Y between the rotation axis R3, R4, or R5 and theacceleration sensor 107 is stored in advance in the ROM of the memory109 of the smartphone 200.

In a case where it is determined that the difference is less than thethreshold value TH (step S31: YES), the corrector 12A calculates theshift blur amounts Sx and Sy by using both the first radius of gyrationLx and the second radius of gyration Ly calculated in step S30 (stepS32). The calculation method herein is the same as that of step S7 ofFIG. 8.

In a case where it is determined that the difference is equal to orgreater than the threshold value TH (step S31: NO), the corrector 12Adetermines whether or not the first distance px is greater than thesecond distance py (step S33).

In a case where the first distance px is greater than the seconddistance py (step S33: YES), the corrector 12A calculates the shift bluramounts Sx and Sy by using only the first radius of gyration Lxcalculated in step S30 in the same method as step S9 of FIG. 8 (stepS34).

In a case where the first distance px is less than the second distancepy (step S33: NO), the corrector 12A calculates the shift blur amountsby using only the second radius of gyration Ly calculated in step S30 inthe same method as step S10 of FIG. 8.

The corrector 12A calculates the shift blur amounts Sx and Sy in stepS32, step S34, or step S35, and corrects the shift blur of the capturedimage signal output from the image sensor 20 by controlling the imageblur correction mechanism 3 so as to cancel the shift blur amounts Sxand Sy (step S36).

According to the smartphone 200, in a case where the imaging isperformed by operating the touch panel 201, it is determined that thesmartphone can roll-rotate around the rotation axis R5, and the radiusof gyration used in the calculation of the shift blur amounts Sx and Syare selected. In a case where the portrait shooting is performed byoperating the button 202 a, it is determined that the smartphone canroll-rotate around the rotation axis R4, and the radius of gyration usedin the calculation of the shift blur amounts Sx and Sy are selected. Ina case where the landscape shooting is performed by operating the button202 b, it is determined that the smartphone can roll-rotate around therotation axis R3, and the radius of gyration used in the calculation ofthe shift blur amounts Sx and Sy are selected. Thus, the shift bluramounts can be calculated by using the radius of gyration closer to amore accurate value according to the usage state of the smartphone 200,and the shift blur of the captured image signal can be corrected withhigh accuracy.

In the smartphone 200, in a case where it is not possible todiscriminate whether the posture of the smartphone 200 is the portraitshooting posture or the landscape shooting posture in a case where theimaging is performed, the rotation axis R5 set at the center of thedisplay unit 103 is selected.

For example, in a case where it is erroneously determined that theposture of the smartphone is the landscape shooting posture even thoughthe posture is actually the portrait shooting posture, the rotation axisR3 is selected, and thus, the distances between the rotation axis R3 andthe acceleration sensor 107 is greater than the correct distances(distances between the rotation axis R4 and the acceleration sensor107). In such a case, in a case where the rotation axis R5 is selected,the distances between the rotation axis R5 and the acceleration sensor107 approach the correct distances. Thus, even in a situation in whichthe posture cannot be discriminated, it is possible to prevent thecalculation accuracy of the shift blur amounts Sx and Sy from beinglowered, and it is possible to correct the shift blur of the capturedimage signal with high accuracy.

In the operation of FIGS. 13 and 14, step S21 is not essential, and maybe a deleted operation. The rotation axes set in the smartphone 200 maybe only the rotation axes R3 and R4. In the operation of the smartphone200 in the still image imaging mode operation in this case, in a casewhere step S21 and step S22 are deleted in FIGS. 13 and 14 and thedetermination in step S25 is YES, for example, only the correction ofthe translation blur may be performed without calculating the shift bluramounts Sx and Sy.

In the digital camera 100 shown in FIG. 2, for example, it is consideredthat a button for exclusive use of the portrait shooting different fromthe shutter button 102 a is provided on a left side surface of thehousing. In the case of such a configuration, the rotation axis on theassumption of the portrait shooting and the rotation axis on theassumption of the landscape shooting may be set at positions differentfrom the rotation axes R1 and R2 of FIG. 7. In the operation of thedigital camera 100 having this configuration, step S21 is deleted inFIGS. 13 and 14, and the processing of step S22 is changed to theprocessing of selecting the rotation axis R1.

FIG. 15 is a diagram showing a hardware configuration of a smartphone200A which is a modification example of the smartphone 200 shown in FIG.10. The smartphone 200A shown in FIG. 15 is the same as the smartphone200 except that a grip sensor 211 is added.

The grip sensor 211 is a sensor for detecting that the housing of thesmartphone 200A is gripped by the hand, and is, for example, apiezoelectric sensor or the like. The appearance of the smartphone 200Ais the same as that of the smartphone 200.

FIG. 16 is a flowchart for describing an operation of the smartphone200A shown in FIG. 15 in the still image imaging mode. The flowchartshown in FIG. 16 is the same as the flowchart shown in FIG. 13 exceptthat step S40 is added between steps S26 and S27. The processing afterstep S27 shown in FIG. 16 is the same as that in FIG. 14.

As a result of the posture determination in step S24, in a case where itis determined that the posture is the portrait shooting (step S26:portrait shooting), the corrector 12A of the system control unit 1A ofthe smartphone 200A determines whether or not the smartphone 200A isgripped based on an output signal of the grip sensor 211 (step S40).

In a case where it is determined that the smartphone 200A is gripped(step S40: YES), the corrector 12A selects the rotation axis R5 set atthe center of the display unit 103 in step S22.

In a case where it is determined that the smartphone 200A is not gripped(step S40: NO), the corrector 12A selects the rotation axis R4 in stepS27.

Even though the posture of the smartphone 200A is the portrait shootingposture in which the direction Y is the vertical direction, the userperforms the imaging while fixing the smartphone 200A by gripping thesmartphone with a left hand H as shown in FIG. 17 and pressing thebutton 202 a with the right finger in this state in some cases. In sucha case (that is, in a case where the determination in step S40 is YES),since there is a possibility that the smartphone 200A roll-rotatesaround the rotation axis R4 is lowered, it is possible to furtherimprove the accuracy of the shift blur correction by selecting therotation axis R5.

In the motion picture imaging mode of the smartphone 200 or thesmartphone 200A, in a case where the imaging instruction is performedregardless of whether the imaging is the touch imaging, button imaging,or any imaging of the portrait shooting and the landscape shooting, itis preferable that the corrector 12A selects the rotation axis R5 andcalculates the shift blur amounts Sx and Sy. Since the smartphone 200 or200A performs the imaging while being gripped by both hands during themotion picture imaging, it is considered that the smartphone 200 or 200Ais likely to roll-rotate around the rotation axis R5. Thus, the shiftblur correction can be performed with high accuracy by selecting therotation axis R5 during the motion picture imaging.

Although it has been described in the digital camera 100, the smartphone200, and the smartphone 200A that the shift blur correction is performedby moving the image sensor 20 by the image blur correction mechanism 3,the present invention is not limited thereto. The image blur correctionmechanism 3 may correct the shift blur by moving a correction lensincluded in the imaging optical system 101 a, or may correct the shiftblur by moving both the image sensor 20 and the correction lens includedin the imaging optical system 101 a. The blur correction may beelectronically performed without optically performing the blurcorrection as in the image blur correction mechanism 3.

As described above, the following matters are disclosed in thisspecification.

(1) There is provided an image blur correction device that corrects ablur of a captured image signal output from an image sensor which imagesa subject through an imaging optical system. The device comprises anacceleration sensor that detects a first acceleration in one directionof two directions which are orthogonal to an optical axis of the imagingoptical system of an imaging apparatus including the image sensor andare orthogonal to each other and a second acceleration in the otherdirection of the two directions, an angular velocity sensor that detectsa first angular velocity of the imaging apparatus around a first axisparallel to the other direction and a second angular velocity of theimaging apparatus around a second axis parallel to the one direction, aradius-of-gyration calculator that calculates a first radius of gyrationof the imaging apparatus around the first axis based on the firstacceleration and the first angular velocity and a second radius ofgyration of the imaging apparatus around the second axis based on thesecond acceleration and the second angular velocity, and a correctorthat calculates a first blur amount of the captured image signal in theone direction generated by rotation of the imaging apparatus around thefirst axis based on the first angular velocity and at least one of thefirst radius of gyration or the second radius of gyration, calculates asecond blur amount of the captured image signal in the other directiongenerated by rotation of the imaging apparatus around the second axisbased on the second angular velocity and at least one of the firstradius of gyration or the second radius of gyration, and corrects thecalculated blur amounts. The corrector selects one rotation axis fromamong a plurality of rotation axes determined in advance parallel to theoptical axis based on a usage state of the imaging apparatus, anddetermines the radius of gyration used in the calculation of the firstblur amount and the second blur amount based on distances in the twodirections from the selected rotation axis to the acceleration sensor.

(2) In the image blur correction device according to (1), in a casewhere a difference between a first distance in the one direction fromthe selected rotation axis to the acceleration sensor and a seconddistance in the other direction from the selected rotation axis to theacceleration sensor is equal to or greater than a predetermined valueand the first distance is greater than the second distance, thecorrector calculates the first blur amount based on the first angularvelocity and the first radius of gyration, and calculates the secondblur amount based on the second angular velocity and the first radius ofgyration.

(3) In the image blur correction device according to (2), in a casewhere the difference is equal to or greater than the value and the firstdistance is less than the second distance, the corrector calculates thefirst blur amount based on the first angular velocity and the secondradius of gyration, and calculates the second blur amount based on thesecond angular velocity and the second radius of gyration.

(4) In the image blur correction device according to (2) or (3), in acase where the difference is less than the value, the correctorcalculates the first blur amount based on the first angular velocity andthe second radius of gyration, and calculates the second blur amountbased on the second angular velocity and the first radius of gyration.

(5) In the image blur correction device according to (2) or (3), in acase where the difference is less than the value, the correctorcalculates the first blur amount based on the first angular velocity andan average value of the first radius of gyration and the second radiusof gyration, and calculates the second blur amount based on the secondangular velocity and the average value.

(6) In the image blur correction device according to any one of (1) to(5), the imaging apparatus comprises an eyepiece window for observingthe subject, the plurality of rotation axes includes a rotation axis setat a position of the eyepiece window and a rotation axis set at the sameposition as the optical axis, and the corrector selects the rotationaxis set at the position of the eyepiece window in the usage state inwhich the subject is observed by using the eyepiece window, and selectsthe rotation axis set at the same position as the optical axis in theusage state in which the subject is observed without using the eyepiecewindow.

(7) In the image blur correction device according to any one of (1) to(5), the plurality of rotation axes includes two rotation axes presentat positions different from the optical axis, and the corrector selectsone of the two rotation axes in the usage state in which the onedirection is a vertical direction, and selects the other rotation axisof the two rotation axes in the usage state in which the other directionis the vertical direction.

(8) In the image blur correction device according to (7), the pluralityof rotation axes includes a rotation axis present at the same positionas the optical axis, and the corrector selects the rotation axis presentat the same position as the optical axis in the usage state in which thestate in which the one direction is the vertical direction and the statein which the other direction is the vertical direction are not able tobe discriminated from each other.

(9) In the image blur correction device according to any one of (1) to(8), the plurality of rotation axes includes a rotation axis present atthe same position as the optical axis, and the corrector selects therotation axis present at the same position as the optical axis in a casewhere the imaging apparatus is set in a motion picture imaging mode, andselects the rotation axis based on the usage state in a case where theimaging apparatus is set in a still image imaging mode.

(10) In the image blur correction device according to (7), the imagingapparatus comprises a display unit provided on surface opposite to theimaging optical system, a touch panel formed on the display unit, and anoperation member provided at a position different from the display unitto give an imaging instruction, the plurality of rotation axes furtherincludes a rotation axis which is different from the two rotation axesand is set at a center position of the display unit, and the correctorselects the rotation axis set at the center position in the usage statein which imaging is performed by operating the touch panel, selects onerotation axis of the two rotation axes in the usage state in whichimaging is performed by operating the operation member and the onedirection is the vertical direction, and selects the other rotation axisof the two rotation axes in the usage state in which imaging isperformed by operating the operation member and the other direction isthe vertical direction.

(11) In the image blur correction device according to (10), in the usagestate in which the state in which the one direction is the verticaldirection and the state in which the other direction is the verticaldirection are not able to be discriminated from each other, thecorrector selects the rotation axis set at the center position.

(12) In the image blur correction device according to (10) or (11), theimaging apparatus comprises a grip sensor detecting that the imagingapparatus is gripped, a longitudinal direction of the display unit iscoincident with the other direction, and a lateral direction of thedisplay unit is coincident with the one direction, and in the usagestate in which the other direction is the vertical direction, imaging isperformed by operating the operation member, and the grip sensor detectsthat the imaging apparatus is gripped, the corrector selects therotation axis set at the center position.

(13) In the image blur correction device according to any one of (10) to(12), the corrector selects the rotation axis set at the center positionin a case where the imaging apparatus is set in a motion picture imagingmode, and selects the rotation axis based on the usage state in a casewhere the imaging apparatus is set in a still image imaging mode.

(14) There is provided an imaging apparatus comprising the image blurcorrection device according to any one of (1) to (13), and the imagesensor.

(15) There is provided an image blur correction method of correcting ablur of a captured image signal output from an image sensor which imagesa subject through an imaging optical system. The method comprises aradius-of-gyration calculation step of calculating a first radius ofgyration of an imaging apparatus around a first axis based on a firstacceleration and a first angular velocity detected by an accelerationsensor that detects the first acceleration in one direction of twodirections which are orthogonal to an optical axis of the imagingoptical system of the imaging apparatus including the image sensor andare orthogonal to each other and a second acceleration in the otherdirection of the two directions and an angular velocity sensor thatdetects the first angular velocity of the imaging apparatus around thefirst axis parallel to the other direction and a second angular velocityof the imaging apparatus around a second axis parallel to the onedirection, and calculating a second radius of gyration of the imagingapparatus around the second axis based on the second acceleration andthe second angular velocity, and a correction step of calculating afirst blur amount of the captured image signal in the one directiongenerated by rotation of the imaging apparatus around the first axisbased on the first angular velocity and at least one of the first radiusof gyration or the second radius of gyration, calculating a second bluramount of the captured image signal in the other direction generated byrotation of the imaging apparatus around the second axis based on thesecond angular velocity and at least one of the first radius of gyrationor the second radius of gyration, and correcting the calculated bluramounts. In the correction step, one rotation axis is selected fromamong a plurality of rotation axes determined in advance parallel to theoptical axis based on a usage state of the imaging apparatus, and theradius of gyration used in the calculation of the first blur amount andthe second blur amount is determined based on distances in the twodirections from the selected rotation axis to the acceleration sensor.

(16) In the image blur correction method according to (15), in thecorrection step, in a case where a difference between a first distancein the one direction from the selected rotation axis to the accelerationsensor and a second distance in the other direction from the selectedrotation axis to the acceleration sensor is equal to or greater than apredetermined value and the first distance is greater than the seconddistance, the first blur amount is calculated based on the first angularvelocity and the first radius of gyration, and the second blur amount iscalculated based on the second angular velocity and the first radius ofgyration.

(17) In the image blur correction method according to (16), in thecorrection step, in a case where the difference is equal to or greaterthan the value and the first distance is less than the second distance,the first blur amount is calculated based on the first angular velocityand the second radius of gyration, and the second blur amount iscalculated based on the second angular velocity and the second radius ofgyration.

(18) In the image blur correction method according to (16) or (17), inthe correction step, in a case where the difference is less than thevalue, the first blur amount is calculated based on the first angularvelocity and the second radius of gyration, and the second blur amountis calculated based on the second angular velocity and the first radiusof gyration.

(19) In the image blur correction method according to (16) or (17), inthe correction step, in a case where the difference is less than thevalue, the first blur amount is calculated based on the first angularvelocity and an average value of the first radius of gyration and thesecond radius of gyration, and the second blur amount is calculatedbased on the second angular velocity and the average value.

(20) In the image blur correction method according to any one of (15) to(19), the imaging apparatus comprises an eyepiece window for observingthe subject, the plurality of rotation axes includes a rotation axis setat a position of the eyepiece window and a rotation axis set at the sameposition as the optical axis, and in the correction step, the rotationaxis set at the position of the eyepiece window is selected in the usagestate in which the subject is observed by using the eyepiece window, andthe rotation axis set at the same position as the optical axis isselected in the usage state in which the subject is observed withoutusing the eyepiece window.

(21) In the image blur correction method according to any one of (15) to(19), the plurality of rotation axes includes two rotation axes presentat positions different from the optical axis, and in the correctionstep, one of the two rotation axes is selected in the usage state inwhich the one direction is a vertical direction, and the other rotationaxis of the two rotation axes is selected in the usage state in whichthe other direction is the vertical direction.

(22) In the image blur correction method according to (21), theplurality of rotation axes includes a rotation axis present at the sameposition as the optical axis, and in the correction step, the rotationaxis present at the same position as the optical axis is selected in theusage state in which the state in which the one direction is thevertical direction and the state in which the other direction is thevertical direction are not able to be discriminated from each other.

(23) In the image blur correction method according to any one of (15) to(22), the plurality of rotation axes includes a rotation axis present atthe same position as the optical axis, and in the correction step, therotation axis present at the same position as the optical axis isselected in a case where the imaging apparatus is set in a motionpicture imaging mode, and the rotation axis is selected based on theusage state in a case where the imaging apparatus is set in a stillimage imaging mode.

(24) In the image blur correction method according to (21), the imagingapparatus comprises a display unit provided on surface opposite to theimaging optical system, a touch panel formed on the display unit, and anoperation member provided at a position different from the display unitto give an imaging instruction, the plurality of rotation axes includesa rotation axis which is different from the two rotation axes and is setat a center position of the display unit, and in the correction step,the rotation axis set at the center position is selected in the usagestate in which imaging is performed by operating the touch panel, onerotation axis of the two rotation axes is selected in the usage state inwhich imaging is performed by operating the operation member and the onedirection is the vertical direction, and the other rotation axis of thetwo rotation axes is selected in the usage state in which imaging isperformed by operating the operation member and the other direction isthe vertical direction.

(25) In the image blur correction method according to (24), in thecorrection step, in the usage state in which the state in which the onedirection is the vertical direction and the state in which the otherdirection is the vertical direction are not able to be discriminatedfrom each other, the rotation axis set at the center position isselected.

(26) In the image blur correction method according to (24) or (25), theimaging apparatus comprises a grip sensor detecting that the imagingapparatus is gripped, a longitudinal direction of the display unit iscoincident with the other direction, and a lateral direction of thedisplay unit is coincident with the one direction, and in the correctionstep, in the usage state in which the other direction is the verticaldirection, imaging is performed by operating the operation member, andthe grip sensor detects that the imaging apparatus is gripped, therotation axis set at the center position is selected.

(27) In the image blur correction method according to any one of (24) to(26), in the correction step, the rotation axis set at the centerposition is selected in a case where the imaging apparatus is set in amotion picture imaging mode, and the rotation axis is selected based onthe usage state in a case where the imaging apparatus is set in a stillimage imaging mode.

(28) There is provided an image blur correction program for correcting ablur of a captured image signal output from an image sensor which imagesa subject through an imaging optical system. The program causes acomputer to execute a radius-of-gyration calculation step of calculatinga first radius of gyration of an imaging apparatus around a first axisbased on a first acceleration and a first angular velocity detected byan acceleration sensor that detects the first acceleration in onedirection of two directions which are orthogonal to an optical axis ofthe imaging optical system of the imaging apparatus including the imagesensor and are orthogonal to each other and a second acceleration in theother direction of the two directions and an angular velocity sensorthat detects the first angular velocity of the imaging apparatus aroundthe first axis parallel to the other direction and a second angularvelocity of the imaging apparatus around a second axis parallel to theone direction, and calculating a second radius of gyration of theimaging apparatus around the second axis based on the secondacceleration and the second angular velocity, and a correction step ofcalculating a first blur amount of the captured image signal in the onedirection generated by rotation of the imaging apparatus around thefirst axis based on the first angular velocity and at least one of thefirst radius of gyration or the second radius of gyration, calculating asecond blur amount of the captured image signal in the other directiongenerated by rotation of the imaging apparatus around the second axisbased on the second angular velocity and at least one of the firstradius of gyration or the second radius of gyration, and correcting thecalculated blur amounts. In the correction step, one rotation axis isselected from among a plurality of rotation axes determined in advanceparallel to the optical axis based on a usage state of the imagingapparatus, and the radius of gyration used in the calculation of thefirst blur amount and the second blur amount is determined based ondistances in the two directions from the selected rotation axis to theacceleration sensor.

Although various embodiments have been described with reference to thedrawings, the present invention is not limited to such examples. It isobvious to those skilled in the art that various changes ormodifications can be conceived within the scope described in the claims,and naturally, these changes or modifications also belong to thetechnical scope of the present invention. The components in theabove-described embodiment may be optionally combined without departingfrom the spirit of the invention.

The present application is based on the Japanese patent applicationfiled on Jun. 27, 2018 (JP2018-122367), the contents of which areincorporated by reference into the present application.

The present invention is highly convenient and effective by beingapplied to a digital camera, a smartphone, or the like.

EXPLANATION OF REFERENCES

-   -   3: image blur correction mechanism    -   20: image sensor    -   100: digital camera    -   101: lens barrel    -   101 a: imaging optical system    -   102 a: shutter button    -   102 b: operation unit    -   103: display unit    -   104: AFE    -   105: image sensor drive unit    -   106: angular velocity sensor    -   107: acceleration sensor    -   108: image processing unit    -   109: memory    -   108 a: finder window    -   108 b: eyepiece window    -   1, 1A: system control unit    -   11, 11A: radius-of-gyration calculator    -   12, 12A: corrector    -   K: optical axis    -   RS: rotation center    -   P: principal point position    -   YJ: first axis    -   XJ: second axis    -   ωx: first angular velocity    -   ωy: second angular velocity    -   Lx: first radius of gyration    -   Ly: second radius of gyration    -   Sx, Sy: shift blur amount    -   θx, θy: rotation angle    -   R1, R2, R3, R4, R5: rotation axis    -   200, 200A: smartphone    -   201: touch panel    -   202: communication unit    -   202 a, 202 b: button    -   211: grip sensor    -   H: left hand

What is claimed is:
 1. An image blur correction device configured tocorrect a blur of a captured image signal output from an image sensorwhich images a subject through an imaging optical system, the devicecomprising: an acceleration sensor that detects a first acceleration inone direction of two directions which are orthogonal to an optical axisof the imaging optical system of an imaging apparatus including theimage sensor and are orthogonal to each other and a second accelerationin the other direction of the two directions; an angular velocity sensorthat detects a first angular velocity of the imaging apparatus around afirst axis parallel to the other direction and a second angular velocityof the imaging apparatus around a second axis parallel to the onedirection; a radius-of-gyration calculator that calculates a firstradius of gyration of the imaging apparatus around the first axis basedon the first acceleration and the first angular velocity and a secondradius of gyration of the imaging apparatus around the second axis basedon the second acceleration and the second angular velocity; and acorrector that calculates a first blur amount of the captured imagesignal in the one direction generated by rotation of the imagingapparatus around the first axis based on the first angular velocity andat least one of the first radius of gyration or the second radius ofgyration, calculates a second blur amount of the captured image signalin the other direction generated by rotation of the imaging apparatusaround the second axis based on the second angular velocity and at leastone of the first radius of gyration or the second radius of gyration,and corrects the calculated first blur amount and the calculated secondblur amount, wherein the corrector selects one rotation axis from amonga plurality of rotation axes determined in advance parallel to theoptical axis based on a usage state of the imaging apparatus, anddetermines the first radius of gyration and the second radius ofgyration used in calculating the first blur amount and the second bluramount based on distances in the two directions from the selectedrotation axis to the acceleration sensor.
 2. The image blur correctiondevice according to claim 1, wherein, in a case where a differencebetween a first distance in the one direction from the selected rotationaxis to the acceleration sensor and a second distance in the otherdirection from the selected rotation axis to the acceleration sensor isequal to or greater than a predetermined value and the first distance isgreater than the second distance, the corrector calculates the firstblur amount based on the first angular velocity and the first radius ofgyration, and calculates the second blur amount based on the secondangular velocity and the first radius of gyration.
 3. The image blurcorrection device according to claim 2, wherein, in a case where thedifference is equal to or greater than the predetermined value and thefirst distance is less than the second distance, the correctorcalculates the first blur amount based on the first angular velocity andthe second radius of gyration, and calculates the second blur amountbased on the second angular velocity and the second radius of gyration.4. The image blur correction device according to claim 2, wherein, in acase where the difference is less than the predetermined value, thecorrector calculates the first blur amount based on the first angularvelocity and the second radius of gyration, and calculates the secondblur amount based on the second angular velocity and the first radius ofgyration.
 5. The image blur correction device according to claim 2,wherein, in a case where the difference is less than the predeterminedvalue, the corrector calculates the first blur amount based on the firstangular velocity and an average value of the first radius of gyrationand the second radius of gyration, and calculates the second blur amountbased on the second angular velocity and the average value.
 6. The imageblur correction device according to claim 1, wherein the imagingapparatus comprises an eyepiece window for observing the subject, theplurality of rotation axes includes a rotation axis set at a position ofthe eyepiece window and a rotation axis set at the same position as theoptical axis, and the corrector selects the rotation axis set at theposition of the eyepiece window in the usage state in which the subjectis observed by using the eyepiece window, and selects the rotation axisset at the same position as the optical axis in the usage state in whichthe subject is observed without using the eyepiece window.
 7. The imageblur correction device according to claim 1, wherein the plurality ofrotation axes includes two rotation axes present at positions differentfrom the optical axis, and the corrector selects one of the two rotationaxes in the usage state in which the one direction is a verticaldirection, and selects the other rotation axis of the two rotation axesin the usage state in which the other direction is the verticaldirection.
 8. The image blur correction device according to claim 7,wherein the plurality of rotation axes includes a rotation axis presentat the same position as the optical axis, and the corrector selects therotation axis present at the same position as the optical axis in a casein which the usage state in which the one direction is the verticaldirection and the usage state in which the other direction is thevertical direction are not able to be discriminated from each other. 9.The image blur correction device according to claim 1, wherein theplurality of rotation axes includes a rotation axis present at the sameposition as the optical axis, and the corrector selects the rotationaxis present at the same position as the optical axis in a case wherethe imaging apparatus is set in a motion picture imaging mode, andselects the rotation axis based on the usage state in a case where theimaging apparatus is set in a still image imaging mode.
 10. The imageblur correction device according to claim 7, wherein the imagingapparatus comprises a display unit provided on surface opposite to theimaging optical system, a touch panel formed on the display unit, and anoperation member provided at a position different from the display unitto give an imaging instruction, the plurality of rotation axes furtherincludes a rotation axis which is different from the two rotation axesand is set at a center position of the display unit, and the correctorselects the rotation axis set at the center position in the usage statein which imaging is performed by operating the touch panel, selects onerotation axis of the two rotation axes in the usage state in whichimaging is performed by operating the operation member and the onedirection is the vertical direction, and selects the other rotation axisof the two rotation axes in the usage state in which imaging isperformed by operating the operation member and the other direction isthe vertical direction.
 11. The image blur correction device accordingto claim 10, wherein, in a case in which the usage state in which theone direction is the vertical direction and the usage state in which theother direction is the vertical direction are not able to bediscriminated from each other, the corrector selects the rotation axisset at the center position.
 12. The image blur correction deviceaccording to claim 10, wherein the imaging apparatus comprises a gripsensor detecting that the imaging apparatus is gripped, a longitudinaldirection of the display unit is coincident with the other direction,and a lateral direction of the display unit is coincident with the onedirection, and in the usage state in which the other direction is thevertical direction, in which imaging is performed by operating theoperation member, and in which the grip sensor detects that the imagingapparatus is gripped, the corrector selects the rotation axis set at thecenter position.
 13. The image blur correction device according to claim10, wherein the corrector selects the rotation axis set at the centerposition in a case where the imaging apparatus is set in a motionpicture imaging mode, and selects the rotation axis based on the usagestate in a case where the imaging apparatus is set in a still imageimaging mode.
 14. An imaging apparatus comprising: the image blurcorrection device according to claim 1; and the image sensor.
 15. Animage blur correction method of correcting a blur of a captured imagesignal output from an image sensor which images a subject through animaging optical system, the method comprising: a radius-of-gyrationcalculation step of calculating a first radius of gyration of an imagingapparatus around a first axis based on a first acceleration and a firstangular velocity detected by an acceleration sensor that detects thefirst acceleration in one direction of two directions which areorthogonal to an optical axis of the imaging optical system of theimaging apparatus including the image sensor and are orthogonal to eachother and a second acceleration in the other direction of the twodirections and an angular velocity sensor that detects the first angularvelocity of the imaging apparatus around the first axis parallel to theother direction and a second angular velocity of the imaging apparatusaround a second axis parallel to the one direction, and calculating asecond radius of gyration of the imaging apparatus around the secondaxis based on the second acceleration and the second angular velocity;and a correction step of calculating a first blur amount of the capturedimage signal in the one direction generated by rotation of the imagingapparatus around the first axis based on the first angular velocity andat least one of the first radius of gyration or the second radius ofgyration, calculating a second blur amount of the captured image signalin the other direction generated by rotation of the imaging apparatusaround the second axis based on the second angular velocity and at leastone of the first radius of gyration or the second radius of gyration,and correcting the calculated first blur amount and the calculatedsecond blur amount, wherein, in the correction step, one rotation axisis selected from among a plurality of rotation axes determined inadvance parallel to the optical axis based on a usage state of theimaging apparatus, and the first radius of gyration and the secondradius of gyration used in calculating the first blur amount and thesecond blur amount is determined based on distances in the twodirections from the selected rotation axis to the acceleration sensor.16. The image blur correction method according to claim 15, wherein, inthe correction step, in a case where a difference between a firstdistance in the one direction from the selected rotation axis to theacceleration sensor and a second distance in the other direction fromthe selected rotation axis to the acceleration sensor is equal to orgreater than a predetermined value and the first distance is greaterthan the second distance, the first blur amount is calculated based onthe first angular velocity and the first radius of gyration, and thesecond blur amount is calculated based on the second angular velocityand the first radius of gyration.
 17. The image blur correction methodaccording to claim 16, wherein, in the correction step, in a case wherethe difference is equal to or greater than the predetermined value andthe first distance is less than the second distance, the first bluramount is calculated based on the first angular velocity and the secondradius of gyration, and the second blur amount is calculated based onthe second angular velocity and the second radius of gyration.
 18. Theimage blur correction method according to claim 16, wherein, in thecorrection step, in a case where the difference is less than thepredetermined value, the first blur amount is calculated based on thefirst angular velocity and the second radius of gyration, and the secondblur amount is calculated based on the second angular velocity and thefirst radius of gyration.
 19. The image blur correction method accordingto claim 16, wherein, in the correction step, in a case where thedifference is less than the predetermined value, the first blur amountis calculated based on the first angular velocity and an average valueof the first radius of gyration and the second radius of gyration, andthe second blur amount is calculated based on the second angularvelocity and the average value.
 20. The image blur correction methodaccording to claim 15, wherein the imaging apparatus comprises aneyepiece window for observing the subject, the plurality of rotationaxes includes a rotation axis set at a position of the eyepiece windowand a rotation axis set at the same position as the optical axis, and inthe correction step, the rotation axis set at the position of theeyepiece window is selected in the usage state in which the subject isobserved by using the eyepiece window, and the rotation axis set at thesame position as the optical axis is selected in the usage state inwhich the subject is observed without using the eyepiece window.
 21. Theimage blur correction method according to claim 15, wherein theplurality of rotation axes includes two rotation axes present atpositions different from the optical axis, and in the correction step,one of the two rotation axes is selected in the usage state in which theone direction is a vertical direction, and the other rotation axis ofthe two rotation axes is selected in the usage state in which the otherdirection is the vertical direction.
 22. The image blur correctionmethod according to claim 21, wherein the plurality of rotation axesincludes a rotation axis present at the same position as the opticalaxis, and in the correction step, the rotation axis present at the sameposition as the optical axis is selected in a case in which the usagestate in which the one direction is the vertical direction and the usagestate in which the other direction is the vertical direction are notable to be discriminated from each other.
 23. The image blur correctionmethod according to claim 15, wherein the plurality of rotation axesincludes a rotation axis present at the same position as the opticalaxis, and in the correction step, the rotation axis present at the sameposition as the optical axis is selected in a case where the imagingapparatus is set in a motion picture imaging mode, and the rotation axisis selected based on the usage state in a case where the imagingapparatus is set in a still image imaging mode.
 24. The image blurcorrection method according to claim 21, wherein the imaging apparatuscomprises a display unit provided on surface opposite to the imagingoptical system, a touch panel formed on the display unit, and anoperation member provided at a position different from the display unitto give an imaging instruction, the plurality of rotation axes includesa rotation axis which is different from the two rotation axes and is setat a center position of the display unit, and in the correction step,the rotation axis set at the center position is selected in the usagestate in which imaging is performed by operating the touch panel, onerotation axis of the two rotation axes is selected in the usage state inwhich imaging is performed by operating the operation member and the onedirection is the vertical direction, and the other rotation axis of thetwo rotation axes is selected in the usage state in which imaging isperformed by operating the operation member and the other direction isthe vertical direction.
 25. The image blur correction method accordingto claim 24, wherein, in the correction step, in a case in which theusage state in which the one direction is the vertical direction and theusage state in which the other direction is the vertical direction arenot able to be discriminated from each other, the rotation axis set atthe center position is selected.
 26. The image blur correction methodaccording to claim 24, wherein the imaging apparatus comprises a gripsensor detecting that the imaging apparatus is gripped, a longitudinaldirection of the display unit is coincident with the other direction,and a lateral direction of the display unit is coincident with the onedirection, and in the correction step, in the usage state in which theother direction is the vertical direction, in which imaging is performedby operating the operation member, and in which the grip sensor detectsthat the imaging apparatus is gripped, the rotation axis set at thecenter position is selected.
 27. The image blur correction methodaccording to claim 24, wherein, in the correction step, the rotationaxis set at the center position is selected in a case where the imagingapparatus is set in a motion picture imaging mode, and the rotation axisis selected based on the usage state in a case where the imagingapparatus is set in a still image imaging mode.
 28. A non-transitorycomputer readable medium storing an image blur correction program forcorrecting a blur of a captured image signal output from an image sensorwhich images a subject through an imaging optical system, the programcausing a computer to execute: a radius-of-gyration calculation step ofcalculating a first radius of gyration of an imaging apparatus around afirst axis based on a first acceleration and a first angular velocitydetected by an acceleration sensor that detects the first accelerationin one direction of two directions which are orthogonal to an opticalaxis of the imaging optical system of the imaging apparatus includingthe image sensor and are orthogonal to each other and a secondacceleration in the other direction of the two directions and an angularvelocity sensor that detects the first angular velocity of the imagingapparatus around the first axis parallel to the other direction and asecond angular velocity of the imaging apparatus around a second axisparallel to the one direction, and calculating a second radius ofgyration of the imaging apparatus around the second axis based on thesecond acceleration and the second angular velocity; and a correctionstep of calculating a first blur amount of the captured image signal inthe one direction generated by rotation of the imaging apparatus aroundthe first axis based on the first angular velocity and at least one ofthe first radius of gyration or the second radius of gyration,calculating a second blur amount of the captured image signal in theother direction generated by rotation of the imaging apparatus aroundthe second axis based on the second angular velocity and at least one ofthe first radius of gyration or the second radius of gyration, andcorrecting the calculated first blur amount and the calculated secondblur amount, wherein, in the correction step, one rotation axis isselected from among a plurality of rotation axes determined in advanceparallel to the optical axis based on a usage state of the imagingapparatus, and the first radius of gyration and the second radius ofgyration used in calculating the first blur amount and the second bluramount is determined based on distances in the two directions from theselected rotation axis to the acceleration sensor.